Leuchter is one amazing guy. This is a guy who became one of the US's foremost experts on death engineering - he designed and built/rebuilt several execution devices for death rows throughout the nation. Then, tragically, he took it upon himself to travel to Auschwitz and hammer bits off the gas chambers to bring home for cyanide testing. His conclusion: no-one was gassed there. Oops. Then he compounded his mistake by testifying for Ernst Zundel and speaking at holocaust-revisionist meets throughout the world.
So, an excellent subject for a movie, and Morris does an okay job. There are a few faults. The quality of some of the interview footage is quite poor. And there is the question of the reconstructions. Leuchter provided Morris with plenty of "home movies" which are incorporated into the film, so the function of the reconstructions seems merely to be to reinforce in our minds the dramatic qualities of a lot of the actions Leuchter performed. Personally, I could've done without them.
10/10 for the subject, 6/10 for the film-making, gives 8/10 overall.